【作者】 任志贵；

【导师】 陈进；

【作者基本信息】 重庆大学 ， 机械设计及理论， 2014， 博士

【摘要】 作为典型的机电液一体化产品，挖掘性能是挖掘机的核心性能指标，对挖掘性能的研究是实现机械、液压和控制系统性能匹配的前提，更是实现液压挖掘机节能、高效和智能化的基础。国内外众多学者针对挖掘性能的研究取得了很多成果，也存在一些不足。这些不足主要体现在以下方面：①现有方法并不能解决实际挖掘过程中挖掘阻力的准确求解问题；②强度分析结果与实际失效形式不符，缺乏对工作装置动静态强度分析的有效方法；③现有理论挖掘力模型无法得到挖掘机在极限挖掘工况下所能发挥的最大挖掘力，也不能针对复合挖掘工况的挖掘能力进行有效评估；④现有图谱分析法不能对挖掘性能作出准确的评价。为解决这些问题，本文主要针对实际挖掘过程中挖掘阻力模型、应力和挖掘阻力测试平台、动静强度分析和验证方法、理论挖掘力建模和挖掘性能分析方法等方面进行了理论与实验研究。本文的具体工作和研究成果主要包括以下内容：1)基于平面力系原理，提出一种将挖掘阻力系向切削刃合成为切向阻力、法向阻力和阻力矩的方法，使挖掘阻力的准确求解成为可能。建立液压挖掘机运动学和动力学模型，结合挖掘阻力系合成结果，提出实际作业过程中挖掘阻力准确求解的测试计算方法，突破了利用经验公式和模拟方法预测挖掘阻力大小的现状，使斗形装置实际作业中挖掘阻力特性分析成为可能，为挖掘性能相关研究奠定理论基础。2)建立液压挖掘机工作装置姿态、应变和油压的同步采集测试平台，并完成多次挖掘过程中多种数据的采集、转换和拟合。利用测试数据和挖掘阻力模型，计算各种挖掘工况对应的挖掘阻力，根据应力应变关系计算所有测点在挖掘过程中的当量应力，为挖掘阻力特性研究和应力结果对比提供实验依据。3)对比实际挖掘过程的动应力峰值与相同挖掘姿态下的静应力仿真值，分析静强度计算结果与真实动应力之间的关系，研究液压挖掘机工作装置广义动载系数的范围，提供一种利用静强度分析手段解决动载荷问题的方法。4)利用实验测试数据，基于达朗贝尔形式的挖掘阻力模型，计算出动臂和斗杆各个铰点在实际挖掘过程中的载荷谱。将其作为外载，利用瞬态分析方法仿真动臂和斗杆整体动应力分布规律。对比动应力的测试与仿真结果，不但验证了瞬态分析过程的正确性，找到一种动强度分析的可行方法，也验证了挖掘阻力模型的正确性。5)利用实际挖掘过程中挖掘阻力的测试计算结果，从总体特性、力值大小和方向特性3个方面分析挖掘阻力各个部分的变化规律，基于统计学原理研究阻力系数、阻力矩系数、阻力角、差值角的主值区间和概率密度。研究斗形装置在真实作业过程中的挖掘特性和挖掘阻力变化规律，为工作装置的设计、优化和理论挖掘力模型的建立提供实验依据。6)基于挖掘阻力的总体特性和力值大小特性提出极限挖掘力的概念和计算模型，解决了现有理论挖掘力模型无法计算出挖掘机本身在单独挖掘工况下所能发挥的极限挖掘力问题；基于复合挖掘过程中挖掘阻力的方向特性，提出并建立了复合挖掘力的概念和模型，为复合挖掘过程挖掘能力的评价提供一种方法，突破现有理论，奠定了液压挖掘机挖掘性能准确评价的理论基础。7)突破以挖掘姿态为研究对象的传统方法限制，提出基于工作域的图谱分析法。该方法从根本上避免了因一个挖掘点对应多种挖掘姿态而带来的问题。以挖掘阻力的测试计算结果为基准，对比基于工作域的图谱分析法与传统方法，结果表明：基于工作域的图谱分析法能够更为准确的反映所在挖掘点的挖掘能力，基于此得到的挖掘力图和挖掘限制图揭示了挖掘力及其限制因素的区域性分布规律，能够准确展现液压挖掘机的挖掘性能。利用基于工作域的图谱分析法研究了4种吨位相近的中型反铲液压挖掘机的挖掘性能，分析过程显示该方法不仅可以提供较为直观的理论挖掘力及其限制因素分布图，还可以提供挖掘力和限制因素比例的统计结果，为液压挖掘机挖掘性能的分析和评价提供了理论依据，为实际的工程应用提供了可靠的方法。更多还原

【Abstract】 As a typical hydraulic mechatronics machine, digging performance is the coreproperty indicators of excavators. Research on digging performance is not only aprerequisite to match mechanical, hydraulic and control system, but also a basis forobtaining energy saving, high efficient and intelligent excavators. Scholars from homeand abroad have made much progress on research of digging performance. But there aresome drawbacks as following:①the current methods can’t solve the accurate diggingresistance in actual digging process.②The unconformity between the strength analysisand the actual failure mode means that more effective methods for working device staticand dynamic strength analysis are required.③The maximum digging force at the limitconditions can’t be acquired from the existing theoretical digging force model, and themodel is not capable to evaluate digging capabilities of compound digging conditions.④The existing pattern analysis method can’t make accurate assessment of diggingproperties. To solve these problems, this paper presents such theoretical andexperimental researches including digging resistance model in actual digging process,test platform of stress and digging resistance, strength analysis and verification methodsof static and dynamic strength, modeling of theoretical digging force and analysis ofdigging performance. Specific work and results of this study include the followings:1) Based on the principle of planar force system, the mechanical model in whichdigging resistance system was composed by the tangential resistance, normalresistance, and moment of resistance on the cutting edge was proposed, whichmakes it possible to attain exact digging resistance. Combined with kinematic anddynamic models of hydraulic excavators, the computational model was built forsolving digging resistance in actual digging process. It abandons the condition ofusing empirical equation and simulation methods to predict the digging resistance,and makes it possible to analyze digging resistance of working device in realworking process, which provides theoretical basis for relevant researches ondigging performance.2) Synchronous test platforms were built to test the working device attitude, stress andhydraulic cylinder pressure of hydraulic excavator. Then the collection, conversionand fitting of data in several digging process were finished. The correspondingdigging resistance in different conditions was calculated utilizing the test data and the digging resistance model. The equivalent stress of all the test points wascalculated based on the stress-strain relationships. These results provide basis forthe research on digging resistance properties and comparison of stress results.3) The peak values of the dynamic stress in actual digging process and staticsimulation stress under same working device attitude was compared, therelationship between static strength and real dynamic stress was summarized, andthe range of general dynamic load factor was researched. These processes provide afeasible way to solve dynamic load problem in static strength analysis way.4) The dynamic load spectrum of each hinge points of boom and arm in actual diggingprocess was calculated by solving the digging resistance model which based ond’Alembert principle with the data obtained from test. Taking it as the external load,the overall distribution of dynamic stress at arm and boom was simulated withtransient analysis method. Dynamic stress gained from transient analysis anddynamic testing was compared. The comparison of stress from test and simulationnot only verifies the validity of transient analysis process, which is a feasiblemethod for dynamic analysis of structures, but also demonstrate the correctness ofdigging resistance model.5) The rules of overall characteristics, force value and direction features of the diggingresistance were researched by studying the experimental result. In addition, basedon statistics theory, the main range and probability density of resistance coefficient,resistance moment coefficient, resistance angle and difference angle were obtained.Research on digging properties and the changing law of digging resistance in realworking process will benefit a lot in designing and optimizing of working deviceand setting up the theoretical digging force model.6) The concept of limiting digging force and calculation model was proposed based onthe overall characteristics and change law of the digging resistance, which makes itpossible to evaluate the limiting digging ability of the excavator exactly. Based onthe direction features of the digging resistance during the process of compounddigging, the concept of compound digging force, as a new way of assessing diggingperformance in compound digging process, was proposed, and the break throughprovides an evaluation methodology for the digging ability in the process ofcompound digging.7) A new method called atlas analysis based on workspace was put forward as asubstitute for the traditional method in which the digging attitude was the focus. The method can avoid the problem that one digging point may correspond to manydigging gestures in traditional method. Based on the digging resistance from thetest result, the atlas analysis based on workspace and the traditional method wascompared. The results show that the atlas analysis based on workspace is moreaccurate in reflecting the digging ability at certain point, since the digging atlas canobviously disclose the regional distribution law of digging force. Utilizing atlasanalysis method based on workspace, digging performance analysis of fourmedium-sized hydraulic backhoe excavators of similar tonnage suggests that thismethod can not only give a more intuitive vision in theoretical digging force andconstraints factors distribution, but also provide statistical results of digging forceand constraints proportion. This method is valuable as theoretical basis forexcavators’ evaluation and analysis and provides a reliable way for engineeringapplication.更多还原